Decolorization of various azo dyes by bacterial consortium

This study was taken up to enrich and isolate bacterial strains capable of decolorizing azo dyes present in soil/sludge samples collected from waste disposal sites of local textile industries. Four bacterial isolates identified as Bacillus cereus (BN-7), Pseudomonas putida (BN-4), Pseudomonas fluorescence (BN-5) and Stenotrophomonas acidaminiphila (BN-3) capable of completely decolorizing C.I. Acid Red 88 (AR-88), were used to develop consortium designated HM-4. The concerted metabolic activity of these isolates led to complete decolorization of AR-88 (20 mg L−1) in 24 h, whereas individual cultures took more than 60 h to achieve complete decolorization of the added dye. The consortium was screened for its ability to decolorize different concentrations of other commonly used azo dyes in addition to AR-88. It was able to decolorize 78% of C.I. Acid Red 88, 99% of C.I. Acid Red 119, 94% of C.I. Acid Red 97, 99% of C.I. Acid Blue 113 and 82% of C.I. Reactive Red 120 dyes at an initial concentration of 60 mg L−1 of mineral salts medium (MSM) in 24 h. This consortium will be used to develop bioreactor for achieving effective decolorization of textile industry effluent containing mixture of azo dyes.